This investigation represents secondary analysis of several large-scale data sets centering on, or containing information relevant to, the self-concept. The present analytic focus is on self-concept change and development. Analysis of a sample of 1,988 public school pupils ranging between grades 3-12 reveals striking changes in desired occupational selves with age. Contary to expectation, occupational self-concepts are more salient to younger than to older children. Second, younger boys are more likely than older to select manual occupations, less likely to choose professional occupations. Third, boys' and girls' occupational selves follow different trajectories; the boys rise from low to very high whereas the girls decline from fairly high to middle level occupations. Fourth, occupational sex-typing remains very powerful throughout the age span. Mutual interaction studies have also been conducted. Cross-lagged panel analyses shown that self-esteem has a greater effect on delinquency than the other way around; self-esteem is also the more powerful variable in explaning the self-esteem/school marks relationship.